Satellite and radar surveillance is being stepped up in the hunt for flight MH370 as the investigation into the missing plane enters its 11th day.

Eleven days after contact was lost with the Boeing 777, authorities have made little progress in working out what happened or where the plane ended up.

At a news conference this morning, Malaysia's Transport Minister Hishammuddin Hussein said the air and surface search area was being expanded and that more countries had been asked to examine radar data.

China's foreign ministry spokesman, Hong Lei, announced it had moved 21 of its satellites in positions where they can search for the missing plane.

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"China has deployed over 10 professional search vessels that are conducting work at related seas and has asked passing Chinese merchant ships to join in the search," he said.

"We have mobilised many aircraft as well as 21 satellites to participate in the search. We have notified 25 countries and briefed them on the relevant situation and asked them adequate consolation."

Signals sent from the aircraft suggest its last position could be anywhere along two corridors stretching from Central Asia to the southern reaches of the Indian Ocean.

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Deep-ocean surveillance capabilities are also being deployed which could locate the aircraft's black box flight recorder assuming the aircraft crashed into the sea.

The hunt now comprises an area 2.24 million square nautical miles (7.7 million square kilometres) - slightly larger than the size of Australia. More than half of the search area is in the remote seas of the southern corridor.

David Cameron telephoned the Malaysian Prime Minister Najib Razak to offer Britain's help in the search, the first such contact between the two countries since the crisis began.

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Meanwhile, angry relatives of Chinese passengers on the plane say they will go on hunger strike if they do not get more information from Malaysian authorities.

"Relatives are very unsatisfied. So you hear them saying 'hunger strike'," Wen Wancheng, whose son was aboard the missing flight, told reporters at the Beijing hotel where families are gathered.

Malaysia Airlines chief Ahmad Jauhari Yahya said at this morning's conference that they had provided care assistants and were doing all they can to look after family members.

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China's state media has been vocally critical of Malaysia's handling of the investigation, saying valuable time and resources were wasted in the hours and days immediately after the aircraft disappeared on March 8.

Malaysia's former transport minister Ong Tee Keat has told Sky News the International Civil Aviation Organisation (ICAO) - a UN body - should take on the probe to ensure there are no cover-ups or withholding of information.

He said he was not alleging a cover-up, but said transparency is needed.

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Gallery: Bodyguards' Air-Security Training

Inspired by the disappearance of flight MH370, the Tianjiao bodyguard academy in Beijing teaches trainees evacuation and close-quarter combat skills to emphasise the importance of aviation safety.

He also said better coordination is needed among Malaysian government agencies and between countries to help find the plane.

Authorities believe someone on board the flight intentionally switched off two vital pieces of communication equipment and deliberately diverted the aircraft. Satellite data suggests the plane flew for at least seven hours.

Background checks on all 154 Chinese passengers have not uncovered any evidence suggesting a plot to hijack or bring down the aircraft, Huang Huikang, the Chinese ambassador to Malaysia, said.

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It appears to discount one theory that Uighur separatists - the group blamed for an attack in Beijing's Tiananmen Square last October and the massacre at Kunming railway station earlier this month - might have been involved in the plane's disappearance.

Investigators continue to probe the background of pilots Zaharie Ahmad Shah and Fariq Abdul Hamid, as well as ground engineers who worked on the aircraft before it took off.

But Malaysian opposition leader Anwar Ibrahim has posted a statement on his blog deploring reports that the pilot of MH370 may have been a political fanatic and responsible for the plane's disappearance.

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"I cannot express enough my disgust to those who are so ready, in the absence of any proof whatsoever, to pin the blame on Captain Zaharie," he wrote.

"I would like to express my deepest sympathy to his wife and children and his family too and to tell them to remain strong in these most trying times. The same goes for all the passengers and crew of flight MH370".

The Malaysian Airlines chief executive also said this morning that neither pilot had experience flying the northern or southern corridor with the airline.

"As far as the pilots, we're looking at the northern corridor, we do not fly there at all, as a commercial airline," he said.

"The southern corridor obviously, unless you fly to the islands and we don't fly to any of the islands."

There has been no trace of the Boeing 777 since it disappeared less than one hour into its flight from Kuala Lumpur to Beijing with 239 people on board.